Thailand allows tourists from 64 countries to enter Thailand without a visa. They are granted to stay a maximum of 30 days if they are entering Thailand via an international airport or entering through a land border checkpoint from neighboring countries.
Under the new provisions of the VISA EXEMPTION RULE and BILATERAL AGREEMENT effective December 31, 2016, passport holders of 64 countries are entitled to enter Thailand under the rule and criteria provided. Please check the countries list and more details at Thai Embassy.

Visa on Arrival

The VISA ON ARRIVAL allows passport holders of 19 countries to enter Thailand under this rule provided that they meet these requirements:

• The visit is strictly for tourism purposes.
• The passport must be genuine and should be valid for at least 30 days.
• You must have a valid address in Thailand whether a hotel or apartment that can be verified.
• You must have a confirmed return ticket to show that they are flying out of Thailand within 15 days of entry, as appropriate. Open tickets do not qualify. Travelling overland out of Thailand by train, bus, etc. to Cambodia, Laos, Malaysia (including a route to Singapore), Myanmar, etc. is not accepted as proof of exiting Thailand. You may be asked to show your flight ticket on entering Thailand. If you do not possess a flight ticket to show that you will be exiting Thailand within 15 days of entry you will be most likely refused entry.
• It will also be necessary to prove that you have funds of at least 10,000 THB per person and 20,000 THB per family during your stay in Thailand.
• A fee of 2,000 THB is payable upon entry and is subject to change without notice. It must be paid in cash and Thai currency only.

Please check the countries list and more information of Visa on Arrival here: https://www.thaiembassy.com/thailand-visa/visa-on-arrival

However, persons who are not eligible to enter Thailand under the VISA ON ARRIVAL and VISA EXEMPTION RULE are advised to obtain visas with the Royal Thai Embassy prior to their visit.